Known turbine assemblies generally include rows of circumferentially spaced turbine blades. Generally described, each turbine blade includes an airfoil extending outwardly from a platform and a shank with a dovetail extending inwardly therefrom. The dovetail is used to mount the turbine blade to a rotor disc for rotation therewith. Known turbine blades generally are hollow such that an internal cooling cavity may be defined through at least portions of the airfoil, the platform, the shank, and the dovetail.
Temperature mismatches may develop at the interface between the airfoil and the platform and/or between the shank and the platform because the airfoil portions of the blades are exposed to higher temperatures than the shank and the dovetail portions. Over time, such temperature differences and associated thermal strains may induce large compressive thermal stresses to the blade platform. Moreover, the increased operating temperatures of the turbine as a whole may cause oxidation, fatigue, cracking, and/or creep deflection and, hence, a shorten useful life for the turbine blade. The potential stresses to the overall turbine blade and the bucket platform in particular generally increase with higher turbine combustion temperatures.
There is thus a desire for a turbine blade with improved cooling, particularly about the suction side of the platform. Such an improved turbine blade design would allow for the use of higher combustion temperatures and, hence, higher overall system efficiency with increased component lifetime.